Analytic solutions of longitudinal and cross waves in the wave flume with an exponential symmetric shoal
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摘要: 水槽实验通常用于波浪传播变形及防波堤护面块体稳定性等研究,涉及的波要素沿水槽纵向变化且在垂直于水槽的横向保持不变。然而实验中当波长与水槽宽度满足一定关系时,可能出现明显的横向波动现象。本文针对对称指数型隆起地形,基于线性长波方程分别推导了其内沿水槽方向的纵波与垂直于水槽方向的横波的解析表达。水槽内对称指数地形上的纵波可以表示为第一类和第二类一阶贝塞尔函数的形式,并结合自由水面及速度连续条件最终得到其完整解。对称指数地形上分别存在偶对称和奇对称模态的横波,可表示为第一类ν阶贝塞尔函数的形式。偶对称模态(n, m)沿水槽方向有n条波节线,在垂直于水槽方向存在2m条波节线;奇对称模态(n, m)沿水槽方向存在n条波节线而在垂直方向有2m − 1条波节线。Abstract: The flume experiment is commonly used to investigate the wave propagation deformation and the stability of the breakwater armor block, with the wave elements changing along the longitudinal direction of the flume while remaining unchanged in the cross direction perpendicular to the flume. However, when the wavelength has a certain relationship with the flume width, visible cross fluctuations may occur. In this paper, the analytical expressions of longitudinal wave along the flume direction and cross wave perpendicular to the flume direction on an exponential symmetric shoal are derived respectively based on the linear long wave equation. The longitudinal waves on symmetric exponential topography in the flume can be expressed as the first and second kinds of first order Bessel function, and the complete solution can be obtained by combining with the conditions of free surface and velocity continuity. Cross waves with even symmetric and odd symmetric modes in the flume with an exponential symmetric shoal can be expressed as the first kind of ν order Bessel function. The even symmetric (n, m) mode has n nodal lines along the direction of the flume and 2m nodal lines perpendicular to the direction of the flume; odd symmetric (n, m) mode has n nodal lines along the direction of the flume and 2m−1 nodal lines in the cross direction.
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Key words:
- cross waves /
- analytical theory /
- wave flume /
- exponential terrain
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图 9 波数κ1 = π m−1、κ2 = 2π m−1、κ3 = 3π m−1时偶对称模态(左侧)和奇对称模态(右侧)横波沿水槽方向的波幅分布
h0 = 0.05 m,h1 = 0.5 m,λ = 0.46 m−1,L = 5.0 m
Fig. 9 Amplitude profiles of cross waves along the wave flume for symmetrical patterns (left column) and anti-symmetrical patterns (right column) with κ1 = π m−1, κ2 = 2π m−1 and κ3 = 3π m−1 respectively
h0 = 0.05 m, h1 = 0.5 m, λ = 0.46 m−1 and L = 5.0 m
图 10 偶对称模态的横波的空间分布
宽2b = 1 m,长L = 5.0 m,顶部水深h0 = 0.05 m,地形参数λ = 0.46 m−1,隆起地形上波数κ2 = 2π m−1,m = 0(a),m = 1(b),m = 2(c)
Fig. 10 Spatial structure of the cross-wave amplitudes for symmetrical patterns over the exponential symmetric shoal
2b = 1 m, L = 5.0 m, h0 = 0.05 m, h1 = 0.5 m and λ = 0.46 m−1 corresponding κ2 = 2π m−1, where m = 0(a), m = 1(b), m = 2(c)
图 11 奇对称模态的横波的空间分布
宽2b = 1 m、长L = 5.0 m、顶部水深h0 = 0.05 m、地形参数λ = 0.46 m−1隆起地形上波数κ2 = 2π m−1,m = 1(a),m = 2(b),m = 3(c)
Fig. 11 Spatial structure of the cross-wave amplitudes for anti-symmetrical patterns over the exponential symmetric shoal
2b = 1m, L = 5.0 m, h0 = 0.05 m, h1 = 0.5 m and λ = 0.46 m−1 corresponding κ2 = 2π m−1, where m = 1(a), m = 2(b), m = 3(c)
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